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In their recently published meta-analyses Brignardello-Petersen et al. (1) concluded that knee arthroscopy including partial meniscectomy for degenerative knee disease provides very small benefits in pain and function over conservative therapy in the short term, but that the evidence fails to support any long term effect. They also claimed that there was no evidence of any subgroup of patients more likely to benefit from the procedure. However, this statement is not substantiated by the results of their systematic review and meta-analysis. Besides, the design of their study is not suited for evaluating subgroups. By making such an unsubstantiated claim, and subsequently adopting it in a clinical practice guideline (2), the risk is that we “throw the baby out with the bath water”.

Despite the accumulated evidence that questions the effectiveness of knee arthroscopy for degenerative meniscus tears, clinical practice does not seem to change.(3-7) Hence, the key question is what information is required in order to effectively change the practice of knee arthroscopy in degenerative knee disease.
Orthopedic surgeons have expressed concerns about the generalisability of the individual trial results, and point out that the study populations may not be representative to the subjects they select for surgery in their day-to-day clinical practice.(8-18) These concerns point to the common perception that some subgroups of patients may still benefit from the procedure. Hen...

In their recently published meta-analyses Brignardello-Petersen et al. (1) concluded that knee arthroscopy including partial meniscectomy for degenerative knee disease provides very small benefits in pain and function over conservative therapy in the short term, but that the evidence fails to support any long term effect. They also claimed that there was no evidence of any subgroup of patients more likely to benefit from the procedure. However, this statement is not substantiated by the results of their systematic review and meta-analysis. Besides, the design of their study is not suited for evaluating subgroups. By making such an unsubstantiated claim, and subsequently adopting it in a clinical practice guideline (2), the risk is that we “throw the baby out with the bath water”.

Despite the accumulated evidence that questions the effectiveness of knee arthroscopy for degenerative meniscus tears, clinical practice does not seem to change.(3-7) Hence, the key question is what information is required in order to effectively change the practice of knee arthroscopy in degenerative knee disease.
Orthopedic surgeons have expressed concerns about the generalisability of the individual trial results, and point out that the study populations may not be representative to the subjects they select for surgery in their day-to-day clinical practice.(8-18) These concerns point to the common perception that some subgroups of patients may still benefit from the procedure. Hence, applying mean effects of trials and meta-analysis to individual patients in day-to-day practice runs against the intuitive approach of doctors to use the specific characteristics of a particular patient to tailor management accordingly. This illustrates the utter importance of a thorough assessment of subgroups while evaluating the effectiveness of the procedure.

Although Brignardello-Petersen et al. (1) acknowledge the apparent clinical importance of possible subgroups, they did not thoroughly evaluate the presence of such subgroups. The authors evaluated differences in outcomes between trials grouped according to blinding and according to the proportion of patients with radiographic osteoarthritis (>50%) only. These limited analyses do not substantiate the claim on the absence of subgroups. It is still possible that there are subgroups of patients who are more likely to benefit from the procedure. To ensure that the guidelines also enjoy the widespread support of clinicians, thorough subgroup analyses will be required evaluating whether selected patients may still benefit from the procedure.

We realize that the identification of subgroups of patients that may benefit from the procedure has been problematic, as the meta-analysis by Brignardello-Petersen et al. (1) was confined to the aggregated data and suboptimal reporting of the original trials, particularly regarding potential subgrouping variables. Just for that reason, the authors should have been more cautious in drawing conclusions with respect to subgroups.

The restrictions imposed by aggregated data and suboptimal reporting in trial reports can be overcome by performing a meta-analysis on the individual original data of trials. An individual participant data meta-analysis (IPDMA) has been described as the gold standard of systematic reviews and meta-analyses. Since IPDMAs include original and more detailed data, they have much more statistical power to carry out informative analyses less prone to bias. Furthermore, by using individual participant data the flexibility of subgroup analyses is enhanced. Consequently, the estimated subgroup effects may be less influenced by misclassification and (ecological) bias. IPDMAs therefore allow a more thorough assessment as to whether differences in treatment effects across subgroups are spurious or not.

Recently we took up the challenge to collaboratively carry out a IPDMA of trials on knee arthroscopy versus non-surgical or sham treatments in patients with knee symptoms and degenerative meniscal tears (PROSPERO CRD42017067240). The objective of this IPDMA is twofold and will be 1) to evaluate the effectiveness of arthroscopic knee surgery with (partial) meniscectomy in comparison with non-surgical or sham treatments in patients with knee symptoms and degenerative meniscal tears, and 2) to identify subgroups of patients who benefit (most) from the procedure. The IPDMA will be conducted by the investigators performing the IPDMA and a steering group including the principal investigators of the original trials that are willing to share their data.
The results of this IPDMA will hopefully form the evidence base to further update and tailor diagnostic and treatment protocols as well as guidelines for patients for whom orthopedic surgeons consider arthroscopic knee surgery.